I wonder what the expected life of the batteries are? I know that some of the early Honda Insights are to the point where they run on gas 90% of the time because the batteries don't hold a charge worth anything now. Honda wants about $4k to replace them too.
So the big question about the Volt is, how long (temporally or mileage-wise) will the Volt be able to get 40 miles on 1 electric 'fill up'? Let say in 8 years, you have to drop $5Gs on batteries because the batteries are only getting you 10 miles....that offsets the savings in fuel quite substantially so it might be ideal to rotate out of this car before that is necessary

. I know you could technically run the car mostly on gas but I'm sure the IC engine in that thing would be very overworked moving that heavy thing around if the electric motor was not running.
And as Michael mentioned, you'd definitely want to run fuel stabilizer in this thing

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EDIT: Ok I see that it says 6000s charge/discharge cycles, so if you drove 40 miles a day and charge it every night, it's going to take 16+ years to hit that point, but as we all know, partial charges (even on lithium ion batteries) have an effect on battery longevity. Time will only tell.